Genetics of fertility restoration of the A5 cytoplasm in pearl millet (Pennisetum glaucum)

For the efficient hybrid seed production, several cytoplasmic-nuclear male sterility (CMS) systems were identified in pearl millet (Pennisetum glaucum (L) R. Br). However, most of the hybrids developed in pearl millet are based on A(1) cytoplasm due to availability of high frequency of restorers in the natural population. This dependence on a single cytoplasm makes any hybrid seed industry vulnerable to disease and insect pest epidemics. A(5) can be a good alternative to A(1) since it is the most stable cytoplasm available. But due to very low frequency (similar to 2%) of restorers available in germplasm, utilization of A(5) cytoplasm in hybrid development had been almost negligible. Restorer breeding efficiency of this CMS system can be significantly increased by understanding the inheritance of fertility restoration by Rf-gene for A(5) cytoplasm, which is poorly studied so far and only one publication is available. Present investigation aims to understand the genetics associated with fertility restoration of the A(5) system of CMS in pearl millet using pollen fertility and seed set percent as a criterion in determining the fertile and sterile plants. Three diverse cytoplasmic-nuclear male-sterile A-lines belonging to the A(5) cytoplasm (ICMA(5)02555, ICMA(5)07999 and ICMA(5)12222) were crossed with two restorer lines (A(5)RT-17/8 and A(5)RT-17/26) to produce 6 F(1)s and their respective F(2)s and backcrosses. These were evaluated for male sterility (S) and fertility (F) at ICAR-IARI, New Delhi during kharif2019 and segregation ratio was established in all the generations chi(2) using test. The segregation pattern of malesterile (S) and male fertile (F) plants observed in F-2 and BC1 indicated dominant single-gene control of male fertility restoration with ICMA(5)02555 and ICMA(5)07999. However, segregation pattern with male-sterile line ICMA(5)12222 had a good fit to 15F:1S ratio indicating two gene control with duplicate interaction. The deviations from the expected ratio with ICMA(5)12222 cross may be due to influence of modifiers. Association between pollen fertility and seed set percent was significant and positive.